This invention relates to a gas insulated electrical apparatus in which electric devices for three phases are housed within a single vessel filled with an electrically insulating gas such as an SF.sub.6 gas.
FIG. 4 is a front view showing partially in section a conventional three-phase gas-insulated switchgear apparatus disclosed in Japanese Patent Laid-Open No. 2-101907 and FIG. 5 is a sectional view of the main portion shown in FIG. 4.
In FIGS. 4 and 5, three circuit interrupters 2a, 2b and 2c for three phases are disposed within a cylindrical vessel 1 in a parallel relationship with a necessary insulating distance A between them. The vessel 1 has shunt pipes 3, 4 and 5 extending in a direction perpendicular to the direction of the row of the circuit interrupters 2a, 2b and 2c and connected to a vessel 6 and 7 containing bus bar disconnectors as well as to a vessel 8 containing cable heads. It is seen that electrical conductors 9 and 10 extend through these shunt pipes 3, 4 and 5 to connect the circuit interrupters 2a, 2b and 2c to the disconnectors and the cable heads.
Since the conventional gas insulated switchgear apparatus has the above-described structure, the cylindrical vessel 1 and the circuit interrupters 2a, 2b and 2c aligned in a row disadvantageously define therebetween spaces B which are unnecessary from the view point of the electrical insulation.
As a measure for minimizing the above spaces B, a gas insulated switchgear structure in which the vessel has an oval-shaped cross section is proposed in Japanese Patent Laid-Open No. 61-191210 for example.
FIG. 6 is a plan view of the gas insulated switchgear apparatus and FIG. 7 is a side view thereof. In FIGS. 6 and 7, the vessels 11, 12 and 13 of an oval cross-sectional shape each containing one of the circuit interrupters for three phases (not shown) are arranged in a row with their longitudinal axes of the oval cross section placed at right angles with respect to the direction of the alignment in the row and a shunt pipe 14 is disposed at the end of each of the vessels 11, 12 and 13 so that an electrical conductor (not shown) may be allowed to extend therethrough for connecting the circuit interrupter to other external electric apparatus.
However, in this arrangement, each of the circuit interrupters for three phases is contained within a respective separate vessel, so that the overall dimensions of the gas insulated switchgear apparatus is disadvantageously large.